1. Field of the Invention:
This invention relates to a protective device for a grinder or the like, and particularly to a protective device which is attached to a concrete grinder, concrete cutting machine or the like for the purpose of preventing concrete swarf particles brought about by grinding or polishing a concrete material from being scatterd in the air.
2. Description of the Prior Art:
Generally, plane grinding or polishing of a workpiece of concrete, for example, has been carried out by use of a grinding or sanding machine having a grinding or sanding wheel composed of abrasives including diamond grains and gives rise to scattering of swarf particles of concrete which tends to injure the health of a worker and invite danger of causing the worker to lose sight of the working portion of a workpiece, thereby decreasing the work efficiency. Though the abrasives such as diamond grains constituting the grinding wheel have of course remarkably high hardness, there is a possibility that the abrasives peel off from one cause or another while grinding and are dispersed in the air, thereby to injure the health of the worker. As one possible way for effectively collecting the swarf particles thus brought about and lessening the danger that the worker carelessly touches the rotating grinding wheel, attempts are now being made to mount a guard cover on the grinding or sanding machine. The guard cover serves to fence about the grinding or cutting wheel and effectively collect swarf particles by imbibing the air around the grinding wheel by suction. In the case where the guard cover made of hard material such as a metal is used, the grinding or cutting wheel has to be exposed in part to the outside of the guard cover. However, if the grinding wheel is put a little out of the guard cover, the work of grinding or cutting often becomes onerous, thereby decreasing the work efficiency is decreased. Otherwise, if the grinding wheel is protruded to excess out of the guard cover to facilitate the grinding work, the guard cover may possibly be deprived of its function as a safeguard. Namely, the adjustment on the guard cover in relation to the grinding wheel turns out to be a very troublesome chore.
In the case of a guard cover made of rubber, for instance, if the grinding wheel should be broken, it is doubtful whether the guard cover can prevent the broken piece from flying apart. Further, the guard cover of rubber is irregularly deformed and suffers a gradual decline in performance due to prolonged use. One example similar to this protective device having such a guard cover has earlier been proposed by the inventor of this invention as a protective device for a grinder or the like in Japanese Utility Model Application Public Disclosure Nos. Sho. 59-24257, 59-66569. The proposed protective device is so designed that the guard cover made of elastic material such as hard rubber encloses the grinding wheel under normal conditions and is elastically contracted to partly expose the grinding wheel in use. However, there is a case where the protective device of this type is unstably deformed as described in the foregoing, whereby the work of grinding becomes relatively troublesome.